Since 2000, NIOSH has conducted a number of epidemiologic studies on respiratory and non-respiratory health in occupants of damp/moldy buildings, and collected more than 2,000 floor/chair dust samples which have been being stored in -80C freezers. The existing database from those studies includes measurements on culturable fungi and bacteria, fungal cell wall components (ergosterol and glucan), and bacterial cell wall components (endotoxin and peptidoglycan) as well as occupants? health. Significant associations between various adverse respiratory and non-respiratory health effects and exposure to fungal biomarkers have been demonstrated. This project examines associations of exposure to mycotoxins with occupants? health by building the capability of analyzing indoor environmental samples for multiple mycotoxins in a single sample analysis. As part of a collaboration with a research group in Austria, approximately 550 floor dust samples are being analyzed and metabolites that are likely to have originated from fungi are being identified. These samples were collected from multiple sources including elementary schools and an office building with a history of water damage. A number of mycotoxins, including sterigmatocystin, zearalenone, roquefortine C, and ochratoxin A were present in the samples at low levels. Surprisingly, 18% of floor dust samples contained deoxynivalenol (vomitoxin; range=4 ? 72 pg/mg of dust), a mycotoxin that can be released from Fusarium graminearum and other Fusarium species. To confirm their findings, NIOSH will compare the results to fungal DNA sequencing data. Using a sample extraction and analysis method for ultra-performance LC-MSMS, NIOSH has been able to simultaneously quantify targeted multiple fungal secondary metabolites in indoor environmental samples. The mycotoxins sterigmatocystin and verrucarol (a hydrolysis product of macrocyclic trichothecene) were measured in culture media samples (rice grains) and filter samples collected in the AGS exposure chamber following inhalation exposures to Stachybotrys chartarum during rodent toxicology studies. An experiment to assess optimal storage conditions for dust samples is ongoing.